A developing method in electrophotography using toner particles coated with a non-volatile liquid

ABSTRACT

A developing powder for electrophotography comprising toner particles coated with a non-volatile substance such as silicone oil, Teflon oil or liquid paraffin which is liquid at normal temperature. The volume resistivity of said liquid substance is above 1 X 1012 Omega cm. and the viscosity is below 1,000 cs. Less than 10 percent by weight of said liquid substance is applied to the toner particles.

United States Patent Matsuo et al. [451 Mar. 28, 1972 [54] A DEVELOPING METHOD IN [56] References Cited ELECTROPHOTOGRAPHY USING UNITED STATES PATENTS TONER PARTICLES COATED WITH A 5 o 3 5/1962 K I 117/ 3,03 0 ess er 100 NON VOLATILE LIQUID 3,234,018 2/ 1966 Wendt..... [72] Inventors: Takehlko Matsuo, Komae Apartment, 17- 3,234,017 2/1966 Heyl ..252/62.]

405, 150, lzumi Komae-cho; Uml Tosaka, Kim Asagaya; Tm mg-W8, FOREIGN PATENTS OR APPLICATIONS Bunka; 00M", 1,077,413 7/1967 Great Britain ..252/62.1 1388, Sanno-cho, Kaminaruko; Takashi 564, Kami Kawasaki-811i, Primary Examiner-George F. Lesmes a l Of T ky Japan Assistant Examiner-J. P. Brammer [22] Filed: No 7 1968 Attamey-Ward, McElhannon, Brooks& Fitzpatrick [21] Appl. No.: 774,065 [57] ABSTRACT A developing powder for electrophotography comprising [30] Foreign Application Priority Data toner particles coated with a non-volatile substance such as silicone oil, Teflon oil or liquid paraffin which is liquid at nor- NOV. 13, Japan mal temperature The vdlume resistivity of said stance is above 1X 10"!) cm. and the viscosity is below 1,000 [52] U.S. Cl. ..1l7/l7.5, 252/62.1, 117/100 C Less than 10 percent by weight of said liquid substance is [5 l ..G03g 9/02, 603g 13/08 applied to the toner panic|es [58] Field ofSearch ..1l7/17.9, 100 C; 252/62.1

4 Claims, 1 Drawing Figure A DEVELOPING METHOD IN ELECTROPI-IOTOGRAPHY USING TONER PARTICLES COATED WITH A NON- VOLATILE LIQUID This invention relates to the improvement of developing powder for electrophotography for developing electrostatic latent images into visible images in electrophotography. More particularly, this invention relates to developing powder which is coated with nonvolatile liquid substance which is liquid form at normal temperature.

Heretofore, developing powder in electrophotography is composed of finely divided resin powder colored with dye or pigment (the granularity thereof being around 101.1,). The colored powder is generally called toner. The toner and a carrier composed of magnetic powder, glass beads or other granular substances are mixed at an appropriate ratio, and the resulting mixture is used as electrophotographic developer. Such electrophotographic developer is used in accordance with a magnet brush process or a cascade process to develop electrostatic latent images into visible image. In accordance with fur brush process, toner alone is used for developing electrostatic latent image into visible image.

The projection of original image onto the photoconductive layer removes the electrostatic charge at the portion exposed to the light, while at the unexposed portion the electrostatic charge remains. The development in electrophotography is generally carried out with a toner which is charged in the positive or in the negative by making use of the potential difference between exposed portions and unexposed portions. Further, the development is carried out by the electrostatic attraction between the surface of photoconductive layer and the toner.

Therefore, the electrostatic attraction between the photoconductive insulating surface and the toner should be large enough to overcome the attraction between the carrier and the toner for carrying out the development.

On the other hand, it is not preferable that toner attaches to the portion where image is not formed, but when electrostatic charge is not perfectly removed by the optical exposure, the toner floating on said portion attaches thereto to produce fog. This phenomenon makes the portion of the photosensitive material which should be, for example, white, into grayish color and the formed image is not easily visible and the visual beauty is disturbed.

Therefore, it is an object of this invention to provide a toner in electrophotography capable of preventing undesirable adhering of toner to a portion where an image is not formed. It is another object of this invention to provide a toner capable of producing fogless and sharp copy. It is a further object of this invention to prevent scattering of toner and unnecessary consumption of toner. lt is still another object of this invention to provide a toner of less secular change. Other objects and advantages will be apparent from the following description and the appended claims.

The new developing powder for electrophotography of this invention is prepared by coating conventional toner particles such as, for example, polystyrene resin, epoxy resin and the like, colored with dyes or pigments, with less than 10 percent by weight on the basis of weight of toner of nonvolatile liquid material having volume resistivity of above IXIO'm cm. and viscosity of below 1,000 cs. which is liquid form at normal temperature, such as, for example, silicone oil, i.e., organopolysiloxanes Teflon oil, trademark for polyfluoroethylene polymers commercially available from Du Pont, liquid paraffin etc.

When the viscosity of the nonvolatile liquid form substance is above 1,000 cs., the coating is difficult, and the adhesion power between the toner and the carrier becomes too great to carry out appropriate by the development. When the volume resistivity is below lXl Q cm., the developed image is electrostatically broken down and unclear image is obtained.

When more than percent by weight of the nonvolatile liquid form substance is used based on the amount of the toner, the adherability thereof is remarkably increased, and

LII

the density of the developed image is lowered, and at the same time, irregularity or such like drawback is produced, and the handling thereof becomes difficult.

According to this invention, the nonvolatile liquid substance at normal temperature coated on toner powder imparts an adsorption force resulting from the adherability of the nonvolatile liquid substance to the toner in addition to the electrostatic attraction force already present between the carrier and the toner. By controlling the adherability of the nonvolatile liquid substance at normal temperature the sum of the two force can be adjusted in such a way that the sum of the forces is less than the electrostatic attraction between the toner and the surface of the photoconductive insulating material which is electrostatically charged while the sum is larger than the electrostatic or physical attraction between the toner and the surface of the photoconductive insulating material which is discharged by optical exposure. As the result, the adhesion of the developing powder to undesirable portions of the surface of the photoconductive insulating material can be completely inhibited and the scattering of developing powder onto other portions of the copying apparatus can be prevented to keep the apparatus clean. Further, adhesion of the developing powder to nonimage portions is inhibited and the resulting image is sharp.

In addition, this invention gives various other advantages such as less secular change and lower consumption of developing powders, high density of image, and wide latitude of ratio of toner to carrier. Heretofore, in the magnet brush process using iron powder carrier of 200-300 mesh the ratio is 2-3 percent, but according to this invention the ratio may be 2-10 percent. Since fog hardly occurs according to this invention, small amount of exposure is enough to obtain images and this effect is substantially the same as sensitization.

In the drawing,

FIG. 1 illustrates diagrammatically an enlarged view of the developing powder of this invention.

Referring now to the drawing, the attached drawing shows the state of toner, and shows how the nonvolatile substance 2 which is liquid form at normal temperature is coated on the surface of the toner l and the toner which looks like mass because of the viscosity of the nonvolatile liquid form substance at normal temperature is separated one by one particle when development is carried .out.

When development is carried out by using the toner of this invention in accordance with magnet brush process, the iron powder carrier of from 50 to 1,000 mesh is employed, and when it is coarser than 50 mesh, the effect of coating is reduced, and when it is finer than 1,000 mesh, the adhesion of the carrier onto the image portion is brought about. The particle size of iron powder carrier is preferably -800 mesh, particularly 200-500 mesh.

The ratio of toner the developing powder to the carrier is from 2 to 10 percent by weight, and when it is below 2 percent, the image density is insufficient and when it is above 10 percent, foggy image is produced.

As the examples of nonvolatile substances which are used in this invention and are in liquid state at normal temperature, silicone oil is particularly preferable as a result of the experiment.

EXAMPLE 1 The toner which was prepared by coloring styrol resin (Piccolastic Dl25 produced by Esso Standard Oil Co., Ltd.) with gilsonite and carbon black, was charged into a vessel, and 10 cs. silicone oil (the trademark thereof being TSP-45 l-lO) was mixed by 5 percent by weight with the toner, and after silicone oil had been perfectly coated on the toner, carrier was mixed therewith, and development was carried out in accordance with magnet brush process, and fogless sharp image could be obtained.

The rate of the toner was 3 percent based on the amount of the carrier.

EXAMPLE 2 The same toner as was used in Example 1 was charged into a V-type mixer, and percent of cs. silicone oil (the trademark thereof being TSF-45l-l0) was mixed with the toner, and in order prevent the solidification of the developer locally by silicone oil, iron or ceramic balls whose diameter is from 5 to 10 mm. were added thereto, and the balls were mixed with the toner for 20 to 30 minutes, and the carrier was added thereto, and thereafter the mixture was passed through the sieve to remove the balls, and development was carried out in accordance with magnet brush process, and fogless sharp image could be obtained.

The rate of the toner was 5 percent based on the amount of the carrier.

EXAMPLE 3 Ten percent of liquid paraffin 2 cs. was coated on the toner in accordance with the same method as in Example 2, and thus obtained product was mixed by 3 percent with a carrier, and development was carried out by using the obtained developing powder in accordance with magnet brush process, and excellent image could be obtained.

EXAMPLE 4 Ten percent of 10 cs. Teflon oil was coated on the toner in accordance with the same method as in Example 2, and thus obtained product was mixed by 3 percent with the carrier, and development was carried out in accordance with magnet brush process, and excellent image could be obtained.

What is claimed is:

l. A process for developing an electrostatic image which comprises contacting a latent electrostatic image with a developer composition comprising an iron powder carrier of All 50-1 ,000 mesh and developer powder composed of toner particles coated with a nonvolatile liquid substance at room temperature selected from the group consisting of liquid organopolysiloxane, liquid polytetrafluoroethylene polymer and liquid parafiin having a volume resistivity of above lXl0"0 cm. and a viscosity of not higher than 1,000 cs., said toner particles being substantially composed of polystyrene resin colored with a dye or a pigment.

2. The developing process according to claim 1 wherein the toner particles are coated with 5-l0 percent by weight based on the weight of the toner of the nonvolatile liquid substance.

3. A magnetic brush developing process for developing an electrostatic image according to claim 8 wherein the iron powder carrier has a mesh of 50l,000 and 2-10 parts by weight of the developer powder are used for each parts by weight of said iron powder carrier.

4. A magnetic brush process for developing an electrostatic image which comprises contacting a latent electrostatic image with a developer composition comprising an iron powder carrier of 50-l,000 mesh and developer powder composed of toner particles coated with a nonvolatile liquid substance at room temperature selected from the group consisting of liquid organopolysiloxane, liquid polytetrafluoroethylene polymer and liquid parafi'in having a volume resistivity of above 1x10" 0 cm. and a viscosity of not higher than 1,000 cs., said toner particles being substantially composed of polystyrene resin colored with a dye or a pigment, and being coated with 5-10 percent by weight based on the weight of the toner of said nonvolatile liquid substance, said developer composition being employed in the ratio of 2-5 by weight of developer powder for each 100 parts by weight of the iron powder carrier.

a: 4: a a

Patent 3,652,315 Dated March 28, 1972.

Takehiko Matsuo et a1. Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the cover sheet insert [73] Assignee: Canon Camera Kabushiki Kaisha, Tokyo, Japan Y Signed and sealed this 27th day of March 1973.

(SEAL) AtteSt:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM PO-1050 (10-69) 6Q376-p59 u.s GOVERNMENT PRINTING OFFICE I969 o-ase-aaa, 

2. The developing process according to claim 1 wherein the toner particles are coated with 5- 10 percent by weight based on the weight of the toner of the nonvolatile liquid substance.
 3. A magnetic brush developing process for developing an electrostatic image according to claim 8 wherein the iron powder carrier has a mesh of 50- 1,000 and 2- 10 parts by weight of the develoPer powder are used for each 100 parts by weight of said iron powder carrier.
 4. A magnetic brush process for developing an electrostatic image which comprises contacting a latent electrostatic image with a developer composition comprising an iron powder carrier of 50- 1,000 mesh and developer powder composed of toner particles coated with a nonvolatile liquid substance at room temperature selected from the group consisting of liquid organopolysiloxane, liquid polytetrafluoroethylene polymer and liquid paraffin having a volume resistivity of above 1 X 1012 Omega cm. and a viscosity of not higher than 1,000 cs., said toner particles being substantially composed of polystyrene resin colored with a dye or a pigment, and being coated with 5- 10 percent by weight based on the weight of the toner of said nonvolatile liquid substance, said developer composition being employed in the ratio of 2- 5 by weight of developer powder for each 100 parts by weight of the iron powder carrier. 